How to Remove Air Bubbles from IPhone Screen Protector?

Yesterday I purchased a Screen Protector for my IPhone 3gs but when I applied it to the screen, there were tiny air bubbles on it.
I Removed the Screen Protector Twice & Applied it again carefully, to see if it works this way but no use. Bubbles were not removed. I've also tried to gently rub the screen, but its useless.

Please tell me How Can I Remove these Air Bubbles?
